@edspencer:
No, there's not much you have to know as normal dev, On the Cake-side you just add the project as plugin, the ExtJS-Side you just add the library. Some samples will follow soon with the first release!
API Docs can be found here: http://docs.banchaproject.org/js/#/api/Bancha

The project is in development, not yet released! The samples aren't working yet!

We had a few issues with mapping in our dispatcher, we're planning to release somewhere in the next two weeks.

On the ExtJS side you just need to use the Bancha API to get models and model data.
Inside CakePHP you just have to create the (almost) standard cake crud methods, description on that will follow soon.